1. Field of the Invention
This invention relates to an air seal and, more particularly, to such a seal for interconnecting a vibrating plenum chamber with a stationary air duct.
2. Description of the Prior Art
It is well known to provide an air drying system to dry particulate materials, such as coal or other crushed or particulate matter, as the material is being conveyed on a vibrating conveyor. To accomplish this, drying air is introduced into the lower plenum chamber of a vibrating conveyor mechanism through inlet air ducts in the side thereof. The air passes upwardly through the vibrating screen panels which comprise the conveying surface and then through the material being conveyed thereon. The passage of air combines with the screen vibration to produce movement of the material along the screen and finally out of the dryer mechanism.
The drying air is delivered to the plenum chamber from a stationary air-conditioning and delivery unit such as an air heater or cooler having a blower fan for circulating the air. This air is transported through a main delivery duct to exit through a plurality of stationary air ducts in communication with the inlet air ducts. Thus, it is seen that some mechanism is necessary to establish a sealed connection for air delivery from the stationary duct to the vibrating chamber.
Heretofore, it has been common practice to provide a flexible interconnecting sleeve, such as a plastic or rubber-coated woven fabric or the like, providing a flexible material with the synthetic coating forming a sealed flexible passage. This sleeve was clamped to the adjacent respective ducts. However, such a flexible interconnector becomes rapidly fatigued, especially if wrinkled or crimped in any manner, resulting in leakage openings developing which in turn results in air loss to the extent the sleeves must be regularly replaced.
The failure rate of the flexible sleeves is aggravated when the drying air is heated to an elevated temperature, which is the most common and efficient drying air. In such instance, the drying capacity of the conveyor is a direct function of the differential in temperatures between the drying air and the ambient air and also the area of the drying screen. As the cost of the conveyor is largely dependent on its size, it is evident that the drying capacity can be increased for a given area by increasing the drying air temperature. However, the operating temperature is determined by the temperature limiting characteristics of the flexible material. Thus, it is common to operate at an air temperature differential of approximately 300.degree.-400.degree. F. although temperature differentials of 600.degree.-700.degree. F. are readily available in the air heater apparatus without much increase in cost. Thus, it is evident that if the interconnecting air seal between the conveyor and the air supply could withstand higher temperatures for longer periods of time, a more efficient and greater capacity drying conveyor could be provided.